Let's start this from the beginning

Swordsmen of the Mist

VI

While Kakashi and Itachi were fortunate enough that Zabuza wasn't all that far away from the city, meaning they wouldn't need to run for too long to reach him, even the half an hour they ultimately required at their top speed was much more than either of them was comfortable with.

What wasn't quite so fortunate, on the other hand, was that they encountered one little problem just before they were about to actually reach their destination.

It happened while they were running through the woods; just when they could feel the trembling ground that must be the result of a nearby explosion, thick mist started to roll towards them, encasing them from all sides. It wasn't an unexpected occurrence, quite the opposite, but it was still rather annoying.

"It seems they want to keep us separated just like last time."

Kakashi, who had come to a stop beside him, nodded. "Obviously." He then pushed his forehead protector up to reveal his blazing Sharingan to match Itachi's already activated ones. "I hate it to play right into their hands, but I'm afraid we don't have much of a choice about this."

He was unfortunately right. In all likelihood, the one who had created the mist was just another water clone that was sent to slow them down while the originals took care of Zabuza. Itachi and Kakashi wouldn't be able to pass here without a fight, but they also couldn't afford it to leave their third teammate on his own for much longer; it was a fair guess to say that the previous explosion was a result of Zabuza's fight, meaning he was still alive, but he would have been forced to fight on his own against two enemies for a while now.

He was in much more danger than either Itachi or Kakashi, so one of them would need to take care of the clone to allow the other to pass.

"Do you-"

"You go," Kakashi interrupted him. "You're faster than I am and Zabuza probably needs help as soon as possible. I have thought of a way to deal with this bothersome technique, so I will join you soon."

Even if Itachi had thought of arguing the point instead of just accepting it, the shuriken flying towards them would have forced them to put an end to it.

Without any further hesitation, Itachi jumped aside to dodge the attack before continuing to run in the direction his crow had been leading them.

Zabuza didn't know exactly how long he ran through the underground complex, avoiding traps and collapsing ceilings as good as he could while growing angrier by the minute, but fact was that his patience had run out quite a while ago. I came here to fight, not to run through empty corridors!

He finally reached his boiling point when he outran yet another attempt at having him buried alive by breaking through a wooden door to escape into the room behind it.

"Kushimaru!" he yelled. "Jinin! I know you bastards can hear me! Stop hiding and face me!"

It was one thing for them to use the Hiding in Mist Technique against him, but this? Trying to kill him by having the ceiling collapse on top of him? That was just insulting! At least the former actually required the user to kill their opponents themselves by using one's skill, but cowardly traps like this were just plain beneath him.

It wasn't that didn't understand that shinobi fought dirty wherever possible. If he were in a position where he could kill his enemies without even getting close to them, he would use it without hesitation as well. However, this wasn't just a fight between random opponents but between Swordsmen of the Mist! If they were to kill each other, then they would do so with their very own hands. Everything else wouldn't be satisfying.

Zabuza knew that his former comrades thought the same, so it made no sense for them to act like this.

As if to confirm these thoughts, slow steps could be heard through the room that Zabuza only now realized was an arena.

"You actually dare to face me for real. Colour me surprised."

"Forgive me, my old friend," Jinin said with a nasty smirk on his face. "I merely wanted to make sure that we wouldn't be disturbed during our fight before we start, and what better way to do so than to destroy every single path that leads to us?"

"So you didn't forget how to speak after all," Zabuza scoffed as he jumped from the gallery he had found himself in into the arena itself. "Say, what would you have done if you actually killed me with that little trick of yours?"

"I don't usually talk with my opponents through one of my clones," Jinin said, realizing that Zabuza was referring to their confrontation a few days ago. "That's just so impersonal, don't you think so too? And regarding your second question, well, I guess then you wouldn't have been worth my time to begin with. Seriously, which good shinobi is crushed by some rocks in a cave!"

He didn't dignify that with a reply. Instead, he looked around the arena. "It has been a while since we were together, hasn't it?" he said. "Where is Kushimaru? I don't think he would be happy to miss this little reunion out."

Jinin snorted. "He was much more interested in your new friends and didn't put much of a fight when I told him I would take care of you on my own. I think he said he wanted to play a bit with that Uchiha brat before finally doing him in." He then shrugged as if to say 'what can you do'. "You know how he gets when Kekkei Genkai are involved."

Zabuza narrowed his eyes in disbelief. "These two have no way to know that I have found you and they will not start to miss me for several hours yet. And even when they do start to miss me, they will still need to actually find us. Are you seriously trying to tell me that Kushimaru plans to sit this out for… what? Perching in a tree for the rest of the day and hope that they somehow find me?"

"Don't act stupid, Zabuza. We know about that crow that has been following both you and the Copy Ninja whenever you left the capital, and that Uchiha brat is famous for using these birds. Do you think we can't put one and one together? We let the bird live and return to its master, so your two new friends will surely arrive here soon."

"Well," he said slowly while hiding just how annoyed he was at them knowing about this little security measure his team had taken. "I guess I should give you guys a little bit more credit. You might be stupid, but there must be a brain somewhere hidden in these thick heads of yours considering you managed to survive for this long."

Rather than offended, Jinin only looked amused. "I went through all the troubles to not only make this an actual one against one battle but also arrange such a nice place for you to die, and yet you still insult me. It seems your manners haven't improved at all since the last time we saw each other."

"Since when did you care about manners? And besides, how can I not insult you when you should know better than this?"

"Know better than what exactly?"

"Isn't that obvious?" Zabuza said with a wide grin while grabbing Kubikiribōchō's hilt. "You should have known better than to challenge me alone and expect to live!"

With that exclamation, he attacked.

Kakashi blocked the shuriken that flew at Itachi's back as he continued forwards with some kunai of his own while simultaneously jumping towards where the projectiles were coming from.

Unlike last time, however, Kushimaru wasn't giving his location away that easily, and what Kakashi found wasn't the man himself but merely a shuriken launcher.

A second after he found it, more shuriken flew at him that were probably fired by similar apparatus.

He continued to dodge these attacks for several minutes with a calm mind while trying to do what Itachi had told him was his plan during his last confrontation with this man and stay on the move. As long as Kakashi didn't stay in one place for too long and didn't let Kushimaru dictate the direction he ran in, his opponent wouldn't be able to use any of his bothersome traps.

However, for some reason, the attacks stayed relatively harmless. Even in this thick mist, it wasn't hard to dodge shuriken and kunai as long as there were only small numbers of them flying at you at once, and as Kushimaru took his time to attack him after each failed attempt, Kakashi hadn't even started to sweat yet. There must be a reason for this, he thought. What is he waiting for?

His question was answered a moment later when he felt murderous intent directed at him from behind, the opposite direction from which the last shuriken had come from.

Kakashi swirled around just in time to block the legendary sword Nuibari that was just about to pierce his abdomen.

Kushimaru -and he was surprised that the man actually attacked him frontal instead of continuing to hide in the mist- didn't let up and continued to attack him:

He ducked beneath the attack to his head and slashed his kunai towards his opponent's torso. Kushimaru dodged it by a hair and sent Kakashi flying with a kick before jumping after him, trying to pierce his heart and almost succeeded hadn't Kakashi been able to redirect the attack upwards just in time to save himself.

Fainting to fall further back, Kakashi then surprised Kushimaru by actually jumping straight at him at the last possible moment; Nuibari, being formed like a needle, could only truly injure an opponent by piercing them, so as soon as Kakashi was within Kushimaru's guard, the weapon became mostly useless.

However, the man was not only aware of this weakness but also an experienced shinobi, so he managed to grab Kakashi's right wrist before the kunai in it could hurt him with his free hand.

Just as Kakashi had expected.

Instead of pushing onward with his attack, he backed away again while simultaneously pulling a small vial with yellowish liquid inside of it from one of his pockets.

A second later, Kakashi escaped once again outside of Kushimaru's reach, the vile in his hand empty now and its content smeared over Nuibari. To no one's surprise, its wielder was once again hiding himself in the mist.

Did he really think I would lower my guard enough after a few moments of harmless attacks for such a weak surprise attack to actually work? Kakashi understood that his opponent was in all likelihood only a clone that was sent to buy the original more time and to keep Kakashi's team separated, but this offence had been much weaker than the one during their last confrontation. Well, I guess this clone does have much less chakra than the last one, so it must be more frugal with it.

However, in the end, it hardly mattered. If anything, his opponent being more limited in its options was a good thing for him. The only thing that truly mattered was that he had successfully managed to complete the first step of his plan.

Kakashi ignored the shuriken flying towards him from his left in favour of turning around and jumping into a seemingly random direction.

A second later, he found himself standing on a tree branch in front of a surprised Kushimaru.

The clone could just so dodge the kunai to its throat but was unable to do anything against the kick against his chest that sent it flying away.

Kakashi didn't bother to follow behind him, though. He could find his opponent with ease now anyway, so keeping track of his location with his other senses was unnecessary. No, all he wanted were a few seconds in which his opponent wasn't watching him. Caught off-guard by his attack as he was, Kushimaru should be distracted enough right now to give Kakashi just that.

Jumping from the tree branch, he went through the necessary hand seals during the short duration of the fall and slammed his hand on the ground as soon as he landed.

"Kuchiyose no Jutsu!" (Summoning Technique)

There was no visible sign that the technique had succeeded, but he knew it did.

He didn't stay where he was for long. His hands had barely touched the ground before he was already on the move again, hurrying westwards towards where he knew his opponent to be.

True enough, he found Kushimaru hiding behind a bush; not giving him any time to react, he instantly went for an attack, for the first time actually pushing his opponent rather than being pressured himself.

Their limbs slammed against crashed against each other, the metallic ring of connecting weapons filled the area, and attacks missed their targets by mere millimetres while Kakashi was steadily pushing his opponent backwards and gaining more and more control over the fight.

Kushimaru's movements became more hectic as the fight went on, and with every passing second, his defence continued to crumble.

Then, Kakashi suddenly stopped.

"What-"

It was a testament to its surprise that the water clone actually spoke when it had remained silent all the time until now, but it never got the chance to finish the sentence because it was at that moment that the ground around his feet broke open, revealing a pack of dogs that fell upon the swordsman and tore him apart.

The clone dissolved shortly after.

Kakashi remained on guard for several more seconds, but when not only the mist began to disperse but also no new attacks were sent his way, he slowly calmed down.

"Good job, buds," he said to the dogs that now sat in front of him with satisfied expressions on their faces. "Seems like our plan worked out just like we hoped it would."

While Kakashi wasn't an Inuzuka, the fact that he used ninja dogs just like they did meant that there were some of their techniques he could use even without being trained in them. Dynamic Marking, being the rather simple but effective trick it was, was one of them.

Kushimaru might have had the foresight to eliminate his smell before facing him, but by using some urine from one of his dogs to mark Nuibari with it, both he and his pack could track the weapon and consequently its wielder with ease wherever he went. It was a shame that he needed to use this technique against a clone instead of the original, but there was no time to lose.

At least the odds were that there hadn't been anyone watching the fight this time, meaning his tactic should still be a surprise if he encountered the real Kushimaru later on.

"Alright," Kakashi continued. "Why don't you guys-"

His eyes widened when he unexpectedly felt the flare of a chakra signature near him, but there was nothing he could do to stop the new figure that appeared in front of him and sliced him open from his navel to his shoulder with a single arc of their sword.

Itachi could hear the clash of weapons when the fight behind him began, but he didn't turn around. He trusted that Kakashi would take care of his opponent and join him soon, and he had his own job to do anyway.

It took less than five minutes to reach the location -a small elevation on an open plain not too far away from the woods he came from- his crow was leading him to. At first glance, there was nothing special about the place, but once he got closer, Itachi realized that the spot where his summon was waiting for him was a little bit different.

"Was here an entrance that has collapsed?"

The crow gave an affirmative croak, confirming his theory.

He couldn't be completely sure, but Itachi would bet that Zabuza had for some reason decided to enter the cave when he suspected their targets to be here instead of first returning to get him and Kakashi and then triggered a trap that collapsed the entrance. That thought made Itachi sigh; while that was definitely in character for the swordsman, he couldn't help but feel a bit annoyed about such reckless behaviour.

Well, nothing he could do about that now. It was much more important to get to him than it was to think about what was and what could have been.

"Doton: Dochū Senkō!" (Earth Release: Subterranean Voyage)

While the entrance had obviously been destroyed, the fact that Zabuza was still alive when he had evidently not been able to escape outside after triggering the trap meant that there must be some kind of underground complex. Thus, all Itachi needed to do to follow his teammate was to 'swim' through the rubble that blocked his way.

Itachi needed a few minutes of searching around until he finally found a corridor; being able to travel through solid rock might be a useful ability, but it had the disadvantage that the only way its users could orientate themselves was through the semantic forces of their opponents. Without that, they were basically blind while in the underground, so as long as there was no one walking through the aforementioned pathway, there was no way for Itachi to be aware of its location. His only choice was to randomly travel through the earth until he found something.

However, his problems unfortunately didn't stop there. Barely five minutes after he had found the corridor, Itachi reached a crossroad with three different paths he could take.

With no sign of which of these paths Zabuza might have taken if he had even been here at all, Itachi decided to create two crow clones to cover all three of them.

He had no idea how long he ran, but he quickly realized that finding Zabuza would be even harder than he had anticipated. Not only was the entire complex absolutely gigantic with new doors and corridors constantly popping up, but there were a lot of recently collapsed ones as well. Itachi had taken that as a good sign at first, but it became soon apparent that many of the collapsed paths were only collateral damage from the few ones that were actually intended to be destroyed, meaning they did not help him find his missing teammate at all. Furthermore, although the subterranean voyage technique wasn't very chakra expensive, using it constantly every time he found a collapsed path would drain his reserves slowly but surely and he couldn't let that happen.

Consequently, all he could do was to search for the slightest signs of Zabuza passing by while stretching his senses in hope of feeling the swordsman's chakra in the distance.

It would be really helpful if there could be another explosion like the one he and Kakashi had heard before they had been separated, but alas, he had no such luck.

Itachi's thoughts came to an abrupt halt when he entered a room that looked like a horror version of an operating theatre; the walls were lined with glass jars containing everything from body parts to dead animals, the floor was covered with dried blood and vomit, the operating table in the centre of the room had straps which were obviously designed to immobilise the 'patient', and the counter next to it held countless tools that looked more suitable for torture than for healing.

Misery and pain were thick in the air and had burned themselves into the room's very walls. Even a blind person who had no idea what was in there would instantly know that something terrible had happened in it and that it had happened for a long time.

The sight gave him a very bad feeling, and a theory began to form in his mind.

For a moment, he considered whether he should go back and try another path. There were no traces that Zabuza had come through here, so he had no reason to continue this way. However, it wasn't like he had a better lead right now, so whether he went back and tried another turn or walked through this room and continued through the door he could at its other end didn't really matter.

Deciding that there wasn't a good reason to backtrack when he could just as well continue onwards, he ultimately chose the latter option.

To Itachi's silent relief, on the other side of that door wasn't anything gruesome to be seen. Just another corridor with even more doors on each side. With how it was connected to that operation theatre, he had expected the worst.

However, three things stood out:

First, the doors here weren't the same wooden constructs he had seen in the rest of the complex so far but strong, heavy-looking metal frames.

Second, this was the first corridor that showed signs of destruction without actually having collapsed completely in that it missed nearly a third of the wall on the right side while debris piled up on the floor in front of the hole.

Third, there was a strange sensation in the air. It almost felt like chakra, but not quite. It was also somewhat familiar, though Itachi couldn't place where he had felt it before. The only thing he knew for sure was that there was something sinister to it, something dark, and that he had to be wary of it.

That conclusion was confirmed a second later when a figure slowly crawled out of the hole in the wall.

All the different pieces are finally in place. The build-up part of this arc is now complete, so the real action can now begin!

Also, I just noted that this story is already over 150k words long. It's quite the achievement if I may say so myself :)